Asthma

Updated Global Inisiative for Asthma Management 2009
Definition
Asthma is a chronic inflammatory disorder of the  airways is associated with airway hyperresponsiveness recurrent episodes of wheezing, breathlessness, chest tightness, coughing


Epidemiology

• >300 million people affected
• One of the most common chronic diseases of childhood, affecting 6 million children
• In children, M>F
• in adults, F>M

Risk Factors

• Host factors: Genetic predisposition, gender, race, body mass index (BMI) (obesity has been associated with higher asthma rates)
• Environmental exposures: Viral infections, airborne allergens, tobacco smoke, etc.
• Patients with food allergies and asthma are at increased risk for fatal anaphylaxis from those foods.

Pathophysiology
Airway narrowing is the final common pathway leading to symptoms & physiological changes in asthma. Several factors contribute to the development of airway narrowing

Airway smooth muscle contraction	in response to multiple bronchoconstrivtor mediators & neurotransmitters is the  predominant mechanism of airway and is largely reversed by bronchodilators
Airway oedema	is due to increased microvascular leakage in response to inflammatory mediators This may be particularly important during acute exacerbations.
AIway thickening	due to structural changes, often termed “remodelling” may be important in more severe disease and is not fully  reversible by current therapy.
Mucus hypersecretion	may lead to luminal occlusion (“mucus plugging”) & is a product of increased mucus secretion & inflammatory exudates

Airway hypersecretion the characteristic functional abnormality results in airway narrowing in a patient in response to a stimulus that would be innocuous in a normal person.

Aetiology/Risk factors

Host factors	Genetic, (e.g.Genes pre-disposing to atopy/airway hyperresponsiveness), Obesity, Sex
Environmetal factors	Allergens Indoor: Domestic mites, furred animals(dogs, cats, mice) cockroach allergen, fungi, molds, yeast Outdoor: Pollens, fungi, molds, yeast Infections (predominantly viral) Occupational sensitizers Tobacco smoke - Passive/Active smoking Outdoor/Indoor Air Pollution Diet

Presentation
Symptoms of recurrent episodes of airway obstruction or airway hyper-responsiveness may include:

• Cough (particularly if worse at night)
• Wheeze
• Chest tightness
• Difficulty breathing

Symptoms are typically precipitated or worsened by exercise, viral infections, irritants such as allergens, changes in weather, stress or strong emotions, and/or menstrual cycles.
Airflow obstruction is at least partially reversible.
Alternative diagnoses are excluded.
May be normal
Focus on:

• General appearance: Signs of respiratory distress such as use of accessory muscles
• Upper respiratory tract: Rhinitis, nasal polyps, swollen nasal turbinates
• Lower respiratory tract: Wheezing, prolonged expiratory phase
• Skin: Eczema

Diagnosis
Often prompted by symptoms:

• episodic breathlessness
• wheezing
• cough
• chest tightness

Assessment of the severity of airflow limitation
Reversibility and variability confirms the diagnosis of asthma
Asthma  severity is measured NOT by severity of the underlying disease BUT its responsiveness to treatment

Classification based on Levels of Asthma Control

Classification in Acute Exacerbation

	MILD	MODERATE	SEVERE	RESP. ARREST IMMINENT
Breathlessness	Walking, can lie flat	Talking infants, softer shorter cry Prefers sitting	At rest infants- stops feeding, hunched forward
Talks in	sentences	phrases	words
Alertness	may be agitated	usually agitated	usually agitated
Resp. rate	Incerased	Increased	*Often >30/min	Bradypnoea
Accessory muscle & suprasternal retraction	None	Present	Present	Present Thoraco-abdominal movement
Wheeze	Audible with stethoscope	Audible with stethoscope	Audible with scope	Absence of wheeze with decreased to absent breathe sounds
Pulses/min	<100	100-200	>120	Bradycardia
Pulsus paradoxus	Absent <10mmHg	May be present 10-20mmHg	Often present 20-40mmHg	Absence suggests repiratory muscle fatigue
PEF %predicted or personal best	>80%	60-79%	<60%
PaO2 RA	Normal test NOT usually neccessary	>60mmHg	<60mmHg Possible cyanosis
PaCO2	<45mmHg	<45mmHg	>45mmHg possible resp. failure
SaO2 RA	>95%	90-94%	<90%

*Normal pulse rate in children

Groups	Age	Normal pulse rate
Infants	2 - 12months	<160/min
Preschool	1 - 2 years	<120/min
School Age	2 - 6 years	<110/min

Hypercapnea (hypoventilation) develops more rapidly in young children

Investigation

Spirometry	Spirometry does not rule out disease Peak expiratory flow rates are inappropriate for diagnosis.
Broncho provocation	(methacholine, histamine, cold air, or exercise) is only definitive diagnostic test.
Allergy skin testing	to evaluate atopic triggers.
Sweat testing	if diagnosis of cystic fibrosis
ABG	for patients with respiratory distress and hypoxia.

Differential Diagnosis

In children	Upper airway diseases (allergic rhinitis or sinusitis) Large airway obstruction (foreign-body aspiration, vocal cord dysfunction, vascular ring or laryngeal web, laryngotracheomalacia, lymph nodes or tumor) Small airway obstruction (viral bronchiolitis, cystic fibrosis, bronchopulmonary dysplasia, heart disease) Other causes (recurrent cough not due to asthma, aspiration/GERD)
In adults	Chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), pulmonary embolism (PE), benign or malignant tumor, pulmonary infiltration with eosinophilia, drugs such as an angiotensin-converting enzyme (ACE) inhibitor, vocal cord dysfunction

Management
4 components

Develop Pt/Dr Partnership	Avoid risk factors Take medications correctly Understand the difference between “controller” and “reliever” medications Monitor asthma control status using symptoms and if available, PEF in children older than 5 yrs of age Recognize signs that asthma is worsening and take action Seek medical help as appropriate
Identify and Reduce Exposure to Risk Factors	Reasonable avoidance measures that can be recommended but have not been shown to have clinical benefit: House dust mites Animals with fur Cockroaches Outdoor pollens and mold Indoor mold Patients should not avoid exercise. Symptoms can be prevented by taking a rapid-acting inhaled B2-agonists before strenuous exercise. Children over the age of 3  with severe asthma should be advised to receive an influenza vaccine  every year, or at least.
Assess, Treat, and Monitor Asthma	Assessing Asthma Control Treating to achieve control Reliever medication Relievers usually come in blue inhalers. Taken as needed (p.r.n) Examples Salbutamol (e.g. Ventolin) and terbutaline (Bricanyl) Ipratropium bromide (Atrovent) is a different type of reliever and is most commonly used by children under two or in older people. Atrovent takes around 45 minutes to work. Inhaled anti-cholinergics S/E: Tachcardia, mild tremor Controller medication Brown inhalers. 2 times a day Examples Inhaled and systemic corticosteroids Leukotriene modifiers Long-acting B2 agonist (LABA) with Inhaled Corticosteroid ICS Sustained release theophyllines Cromones There are 5 treatment steps: Appropriate device used according to  the child’s age: Children younger than 4 yrs old should use a pressurized metered-dose inhalers (pMDIs) plus a spacer with face mask or a nebulizer with a face mask. Children aged 4-6 yrs should use a pMDI plus a spacer with mouthpiece, a DPI,or a nebulizer with face mask Children of any age over 6 yrs who have difficulty using a pMDIs should use a pMDI wit a spacer, a breath-actuated inhaler, a DPI, or a nebulizer Children who are having severe attacks should use a pMDI with a spacer or a nebulizer Monitoring to maintain control Typically, patients should be seen one to three months after the initial visit, and every three months thereafter. After an exacerbations, follow-up should be offered within two weeks to one month. At each visits, the following questions are asked: Is the asthma management plan meeting expected goals? Is the patient using inhalers, spacer, or peak flow meters correctly? Is the patient taking the medications and avoiding risk factors according to the asthma management plan? Does the patient have any concern? Stepping down treatment when asthma is controlled When controlled on medium- to high-dose inhaled glucocorticosteroids:  50% dose reduction at 3 month intervals When controlled on low-dose inhaled glucocorticosteroids:  switch to once-daily dosing When controlled on combination inhaled glucocorticosteroids and long-acting inhaled β2-agonist, reduce dose of inhaled glucocorticosteroid by 50% while continuing the long-acting β2-agonist If control is maintained, reduce to low-dose inhaled glucocorticosteroids and stop long-acting β2-agonist Stepping up treatment in response to loss of control Rapid-onset, short-acting or long-acting inhaled β2-agonist bronchodilators provide temporary relief. Need for repeated dosing over more than one/two days signals need for possible increase in controller therapy Use of a combination rapid and long-acting inhaled β2-agonist (e.g., formoterol) and an inhaled glucocorticosteroid (e.g., budesonide) in a single inhaler both as a controller and reliever is effecting in maintaining a high level of asthma control and reduces exacerbations (Evidence A) Doubling the dose of inhaled glucocortico-steroids is not effective, and is not recommended
Manage Exacerbations	Patient’s should immediately seek medical care if… The attack is severe: The response to the initial bronchodilator treatment is not prompt and sustained for at least 3 hours There is no improvement within 2 to 6 hours after oral glucocorticosteroid  treatment is started There is further deterioration. Prompt treatment for Asthma attacks Oxygen is given if patient is hypoxemic. Deliver by 24% face mask 4L/minute Inhaled rapid-acting B2-agonists in adequate doses (2 begin with 2-4 puffs every 20mins for the first hour; then mild exacerbation will require 2-4 puffs every 3 to 4 hours; and moderate exacerbations 6 to 10 puffs every 1 to 2 hours). If inhalation is not possible, give iv bolus of 5µg/kg over 5 minutes, followed by 5µg/kg/h Ipatropium 2 puffs every 20 minutes for 1st hour only Oral glucocorticosteroids (0.5mg prednisolone/kg) introduced early in the course of moderate or severe attack to help reverse thye inflammation and speed recovery. Aminophyline in ICU: loading dose 6-10mg/kg begin No oral B-agonist or LABA.

Complications
Atelectasis
Pneumonia
Air leak syndromes: Pneumomediastinum, pneumothorax
Respiratory failure
Death:

• Even in patients classified with mild asthma
• Approximately 50% of asthma deaths occur in the elderly (age >65 years) (9).

Prognosis
Risk factors for persistent asthma (in children <3 years of age with ≥4 episodes of wheezing in preceding year): Either history of asthma in ≥1 parent or documented atopic dermatitis or aeroallergen sensitivity
Alternatively, ≥2 of the following will also place these children at increased risk:

• Food sensitivity
• ≥4% peripheral eosinophilia
• Wheezing episodes unrelated to upper respiratory tract infections